Abstract

Noise properties of large-count spectral multicasting in a phase-insensitive parametric mixer were investigated. Scalable multicasting was achieved using two-tone continuous-wave seeded mixers capable of generating more than 20 frequency non-degenerate copies. The mixer was constructed using a multistage architecture to simultaneously manage high Figure-of-Merit frequency generation and suppress noise generation. The performance was characterized by measuring the conversion efficiency and noise figure of all signal copies. Minimum noise figure of 8.09dB was measured. Experimental findings confirm that noise of the multicasted signal does not grow linearly with copy count and that it can be suppressed below this limit.

Figures (6)

The three stage architecture begins with launching two pump waves (black) with the signal (I) into the first stage HNLF. The system is spectrally broadened in this first stage (II), temporally compressed in the single mode fiber (SMF) stage, and injected into the second HNLF stage consisting of dispersion flattened HNLF (DF-HNLF). The DF-HNLF stage generates a comb and multicasts the signal (III). The sideband of interest can then be filtered by an optical bandpass filter (OBPF) and detected (IV). Processing of the detected signal resolves the CE and NF, referenced against the input signal. Red and blue signals correspond respectively to lower sidebands (LS) and upper sidebands (US) as referenced later in the text.

A. The original sinusoid (grey dotted curve) is formed after combining two pump seeds and a signal. Maximally compressed pulses are formed after 105 m HNLF section in the first mixer stage and 4.0 m of SMF in the second, compression stage (heavy solid curve). An attempt to induce higher chirp in longer (300 m HNLF) first stage matched by a 2.96 m SMF compression (light solid curve) leads to effective pulse loss via strong TOD distortion. B. Pulse peak power evolution within the SMF compressor is shown for the 105 m (heavy solid curve) and the 300 m (light solid curve) long first stage.

A. The CE and NF for a simulated parametric multi-casting mixer with 105 m in first stage HNLF, a 4.0 m SMF compressor, and 240 m of DF-HNLF. This fiber system was seeded with 1547.7 nm and 1550.9 nm ideal 29 dBm pumps and a −5 dBm signal laser. The CE shows 100 nm of net positive gain operation. The NF at the center of this regime is 7.4-10.9 dB and < 13 dB near the edge of transparent operation. B. When the multicaster operates in anomalous dispersion (DF-HNLF with peak dispersion at 0.05 ps/nm∙km), net-gain is lost to pump depletion.

The dual-pumped parametric multi-caster was set up with two injection locked CW lasers SL1 and SL2 to generate a 3.2 nm (400 GHz) pitch comb. The injection locking was referenced to a narrow linewidth master CW laser M1 through a 0.2 nm (25 GHz) pitch comb generated by a pair of phase modulators (PM). The locking lines were selected by a programmable OBPF (POBPF). A separate CW signal laser was combined with the two pumps and injected into the mixer system. The output was filtered optically to broadly reject the comb and again to narrowly select the band of interest for detection and CE and NF calculation. The electronic processing was performed with a multi-meter (MM) and electrical spectrum analyzer (ESA).

CE and NF comparison between simulation of a near-optimal case (Section 3) and experiment. Simulation shows CE to be between 2 to 8 dB with a NF from 8.32 dB to 10.88 dB. The post DF-HNLF measurement shows net positive CE across 30 nm and NF less than 10 dB across 20 nm culminating in a minimum NF of 8.09 dB with maximum error +/− 0.6 dB.